1. Field of the Invention
The present invention relates to a temperature compensated magnetoresistive effect thin film magnetic sensor.
2. Description of the Prior Art
Thin film magnetic sensors (MR sensors) utilizing the magnetoresistive effect (MR effect) elements such as Ni-Fe alloy and Ni-Co alloy have been well known but since the resistances of those MR elements are temperature-dependent they need the temperature compensation.
A structure of a conventional temperature compensated thin film magnetic sensor is shown in FIG. 1, in which numeral 1 denotes a glass substrate on which a metal exhibiting the MR effect such as the alloy mentioned above is deposited by a thin film deposition process with a magnetic anisotropic axis thereof being oriented in the direction of an arrow A and tailored by a photolithography technique to form simultaneously a magnetic signal detecting MR element 2 and a temperature compensating MR element 3 spaced therefrom by a predetermined distance.
After the formation of the MR elements 2 and 3, electrodes 4 are electrically connected by the thin film deposition process or the photolithography process to complete the MR sensor.
Before the MR sensor thus formed is packaged, a protective layer is deposited, a cover glass is attached, ends thereof are cut or polished as required.
FIG. 2 shows an exemplary circuit which uses the MR sensor thus formed.
Referring to FIG. 2, MR.sub.1 and MR.sub.2 correspond to the detecting MR sensor 2 and the temperature compensating MR sensor 3, respectively, and Ra and Rb represent resistors. These elements form a bridge circuit as a whole.
A balanced condition of the bridge circuit of FIG. 2 is given by the following formula (1); EQU MR.sub.1 .times.Rb=MR.sub.2 .times.Ra (1)
In the formula (1), when no magnetic signal field is applied to MR.sub.1 at a given temperature, a voltage V is zero, and when a magnetic signal field is applied to MR.sub.1, the resistance of the detecting MR element MR.sub.1 changes so that the voltage V changes to produce an output signal. If the resistance of the temperature compensating MR element MR.sub.2 also changes by the magnetic signal field, an error is produced in the output signal.
Accordingly, in the conventional temperature compensated MR sensor, the detecting MR sensor 2 must be spaced from the temperature compensating MR sensor 3 in order to prevent the resistance of the temperature compensating MR element from being influenced by the external magnetic signal field.
For example, when the detecting MR sensor 2 has a width w of 20 .mu.m and a length l of 150 .mu.m, a spacing p of no less than 250 .mu.m is required between the MR sensors 2 and 3.
As a result, the conventional MR sensor has many defects such as large size, low positional precision of the temperature compensation and a time lag in the temperature compensation.